Friction pad footwear



April 3, 1956 E. R. DYE

FRICTION PAD FOOTWEAR Filed Oct. 19, 1955 Illlllllllllqll IN V EN TOR.

FRICTIN PAD FTWEAR Edward R. Dye, Grchard Paris, N. Y., assignor to Cornell Aeronautical Laboratory, Inc., Buffaio, N. Y., a con poration of N ew York Application October 19, i953, Serial No. 386,797 3 Claims. (Cl. E56-$9) This invention relates to improvements in friction pad footwear to be worn by a person while working on slippery metallic surfaces.

While the friction pad embodying the present invention may be attached to footwear such as worn by sheet metal roofers and the like, it is intended particularly for use by personnel who walk on the aluminum surface of the wing of an airplane to check the oil and till the wing tanks. These surfaces are normally quite slippery and when coated with a thin film of oil or water, become even more slippery. Rubber soles are not satisfactory and nothing can be used, like metal cleats, on the footwear of such maintenance personnel to increase the traction because it would injure the surface of the thin Wing skin.

Accordingly, the principal object of the present invention is to provide a foot pad for use on the bottom surface of footwear, so constructed that the surface of the metal walked upon or stepped on is not dented, scratched or otherwise marred and yet possesses a high coeicient of friction to prevent the person from slipping.

Another object is to provide such a friction foot pad which may be attached to a wide variety of specilic types of footwear.

A further object is to provide such a friction foot pad which is simple in construction and inexpensive to manufacture.

Other objects and advantages will be apparent from the following description and accompanying drawings in which:

Fig. 1 is an elevaitonal view of the side of a wearers foot with shoe thereon and covered by a sandal to which the friction foot pad embodying the present invention is attached, the pad being illustrated under load occasioned by the weight of the wearer thereon.

Fig. 2 is a greatly enlarged vertical central sectional view of the foot pad and showing a fragment of the sandal sole, this view illustrating the condition of the foot pad with no pressure applied thereto and being taken on line 2 2 of Fig. l.

Fig. 3 is a reduced elevational view of the top of the friction foot pad per se, this view being taken on line 3 3, Fig. 2.

Fig. 4 is an elevational view of the bottom of the friction foot pad shown in Fig. 2.

Referring to Fig. l, the friction foot pad forming the subject of the present invention is shown as suitably attached, as hereinafter described, to the bottom surface of the sole of a sandal, preferably made of rubber or other suitable elastic material and having a sheath 11 which tits over the front portion of the wearers shoe and which is held in position thereon by an integral strap 12 which engages the wearers foot slightly above the heel. Such a sandal resembles a half rubber which can be readily slipped on and removed from the wearers shoe. It is to be understood that this slip-on type of shoe covering is merely illustrative of one preferred mode of footwear to which the foot pad may be attached. If de- 2,740,208 Patented Apr. 1956 sired, the friction foot pad may be directly securedto the sole or tread surface of a shoe.

Referring to Fig. 2, the friction foot pad per se comprises a base indicated generally at 13 for attachment to the sole 10, this latter being representative of the sole of a sandal or shoe, and an emery faced deformable member 14 rotatably mounted on the base 13. The base 13 is intended as a rigid structure to provide a flat bearing surface on its lower face on which the member 14 may turn and also is adapted for attachment to a suitable supporting structure such as the sole l0. As shown, the base 13 includes a flat sheet metal disk 15 made of any suitable metal such as aluminum or steel, covered on its upper face with a suitable coating 16 fast thereto, such as provided by a disk of sheet rubber composition cemented to the rigid disk 15. The upper face of the coating 16 in turn is shown as cemented to the bottom surface of the sole, this last mentioned layer of cement being represented by the number i7'. The lower face of the metal disk i5 is smooth so as to minimize frictional resistance to the turning of member ld.

The emery faced deformable member 14 is rotatably mounted on the base 13 by means of a rivet i8 extending centrally through these members. As shown the rivet 18 has a lower enlarged flat button like head i9 which ts against the bottom of the member i4 and a hollow shank, the upper end of which is peened over as indicated at 20 to hold the various components together. As shown, the coating lo has an enlarged central aperture 2l to accommodate the upper rivet head 2Q which head does not extend above the upper surface of this coating.

Before assembly to the base 13, the member 14 is preformed substantially into the shape shown. The member i4 comprises an upwardly cupped or dished disk 22 of substantially uniformly thick iiexible deformable material which is resistant to attack by oil or gas and has a low coefficient of friction on its upper surface. A material which I have found particularly satisfactory is a tough dense synthetic composition of thermoplastic sheet material and chemically described as a copolymer of butadiene and acrylonitrile and styrene and acrylonitrile. Another example of a material suitable for my purpose, produced by a different manufacturer and used as a shoe sole mate rial, is described by such manufacturer as an elastomer resin blend. However, I prefer the first mentioned material. Leather or natural synthetic rubber is unsuited for use as the disk 22 because these materials are either attacked by Contact with oil or gas, or possess too high a coefficient of friction when contacting the opposing face of the metal disk i5, to such an extent as to restrain excessively the turning of the member i4, such turning being desired as hereinafter explained.

Returning to the structural description of the cupped or dished disk 22, the same has its central portion raised as indicated at 23 in Fig. 2 so as to provide an annular gradually rounded downwardly extending salient. The top of the raised central portion 23 is in juxtaposition to the metal disk 15, being held there by the rivet 19 and the annular rim of the dished disk 22 engages the metal disk 1S. Surrounding this central portion 23 adjacent the top thereof is a ring 24 of cushion material such as felt. The lower exposed surface of the preformed member 22, except for the central portion thereof surrounding the lower rivet head 19, is faced with emery cloth indicated at 25. This emery cloth is preferably cemented to the member 22.

The purpose of the felt washer 24 is to provide bulk adjacent the rivet head i9 to prevent the deformable member 14 from attening out completely when the pad is stepped on so that the rivet head will not be pressed into contact with the metal surface being walked on by the wearer. Also, the felt washer 24 tends to restore the ominous -3 preformed flexible member v22 to the shape shown in Fig. iwben' thew'eiglit f the lwearer is'liftd.

VI have found that cloth coated with emery of relatively small grit sizergives excellentV friction on'aluminurn alloy surfaces. Indentations causedby the lgritwill fully recover after .the pressure is remove'djprovided thegrit size is no larger than would pass through a 100 mesh screen. 'In use, the emery grit directly on the sole of a shoe-would cause much abrasion to the wing surfaces because the shoe is rotated `or twisted relative to the surface yas the wearer turns in-performing his work. When rotation of the shoe sole occurs, the friction coefficient would change, of course, from static to kinetic and also the-gritrwould cut into the surface and therefore would be quite objectionable vfor continuous use. in contrast, 4with my present foot pad, the emery cloth remains stationary in relation to 4the wing with the weight of the wearer causing the flexible member 14 to substantially atten against the base 13 while this base revolves about the axis of the rivet 18. Relative rotation is permitted to occur between the opposing surfaces of the metal disk` 15 and tiexible member 22 which have a low coetiicient of friction. The felt washer 24 also 4provides low frictional resistance to turning. Obviously as pressure on the pad increases the flexible member 22 flattens to a greater degree which brings more of the grit side of the emery cloth facing 25 into contact with the metal surface being stepped on. Actual tests have demonstrated that the friction between the 'emery cloth facing of my foot pad is as good on an oiled or wetted metallic surface as that of dry rubber on dry'aluminum.

While the foot pad has been shown as arranged under the forepart of the wearers foot, if desired, a similar foot'pad can be also placed under the heel of the shoe so that while the wearer walks, if the heel comes down first, the heel pad provides a high friction contact.

I claim:

1. A friction foot pad adapted to be attached to the tread surface of footwear, comprising in its unloaded condition a rigid base securable to said surface and yhaving a smooth iiat bottom, an upwardly dished disk member of iiexible sheet material arranged on said bottom of said base and having its annular rim engaging said base, the central portion of said member being raised vand disposed adjacent said base whereby said member has an annular rounded salient adapted to engage the surface stepped on, pivot means connecting said raised central portion 'to said base to allow said member to rotate relative to said base, and a facing of emery cloth fast to the lower surface of said member, said member tending to atten against said base vwhen pressure is applied to urge said member and base together.

2. A friction foot pad adapted to be attachedA towthe "tread surface of footwear, comprising in itsunloaded condition a rigid base securable to said surface and having a smooth iiat bottom, an upwardly dished disk member of flexible sheet material arranged on said bottom of said base and having its annular rim engaging said base, the central portion of said member being raised and disposed adjacent said base whereby said'member has an annular rounded salient adapted to engage the surface stepped on, pivot means connecting said raised central portion. to said base to allow said member to ifotate'r'elative to said base, a washer of lowfriction yielding rnaterial vinteiposed between said member-and -base -and surrounding said raised central portion of saidmember, and a facing of emery cloth'fast to thelower surface of said member, said member tending to atten against said base when pressure is applied to urge said member and base together. l y u 3. A friction foot pad adapted 'to be attachedftothe tread surface of footwear, comprising in its unloaded condition a rigid base including a flat metal disk having a central hole therein and a sheet of rubbercomposition fastened to its upper surface and also having a central but larger hole therein, the upper surface of said sheet being attachable to said tread surface, a dished diskmember of tiexible sheet material arranged on the bottom of said metal disk, the upturned marginal edge of said member engaging said metal disk, said member having a central yraised portion yarranged against said bottom-of said metal disk and having a central hole therein, the portion of said member between said central raised portion and said marginal edge being spaced from said metal disk and gradually curving downwardly from said central raised portion and thence upwardly towardfsaid'marginal edge to provide an annular salient, a at headed rivet arranged in said holes and permitting rotation of said member relative to `'said metal disk, a felt washer interposed between said member and metal disk and surroundingsaid raised central `portion of saidwmember and engagingithe downwardly curving portion of said member, and a facing of emery cloth fast to the lower surface of said-meniber, said salient of said member tending to flatten against said metal disk when pressure is applied to urge said member and base together.

References cited in the me of this patent UNITED STATES PATENTS `1,350,183 VHandi kl''eugio, 1920 1,411,200 `Zertuche i.- Mar. 28, :1 922 2,426,524 Rosenbarger Aug. 2,6, i947 2,671,971 Garretson Mar. 16,1954 

